1. Field of the Invention
The following relates to an image reading device that precisely reads an original""s image data with light passed through the original, and an image reading device that more precisely reads the image data by using invisible light.
2. Description of the Related Art
In recent years, technology has become known wherein frame images recorded on the originals of photographic films and the like are photoelectrically read by reading sensors such as CCDs and the like. Image processing such as enlargement, reduction, various kinds of correction and the like is applied to digital image data obtained by this reading, and images are formed on recording materials by laser light that is modulated on the basis of the processed digital image data.
In technology for digitally reading frame images with these reading sensors such as CCDs and the like, in order to achieve high precision image reading, a frame image is preparatorily read (so-called prescanning). Reading conditions (e.g., the amount of light to shine on the frame image and the charge accumulation time and the like of a CCD) are decided according to density and the like of the frame image, and the frame image is read again under the thus decided reading conditions (so-called fine-scanning).
As a light source for the aforementioned image reading, conventionally, a halogen lamp was used as a general exposure light and the like. Infrared light was removed at a filter and light was sensed as each of three primary colors (R, G, B). Original image reading was performed with respective filters attached at CCDs. At this time, to reduce the effect on image reading of dirt and damage applied to the original, the original was illuminated with diffused light from the light source.
Further, in order to perform image reading at a higher image quality, image reading devices were proposed wherein the original was illuminated with infrared light, and a CCD or the like read the transmitted light. Thus, inappropriate pixels caused by dirt or damage applied to the original were detected, and image-reading data detected for the three primary colors was corrected.
In the image reading devices described above, by convention, halogen lamps and the like were used as light sources. Halogen lamps had the disadvantages of generating large amounts of heat and occupying large spaces. They also required infrared-cut filters, light modulation filters and the like. Thus, they also had the disadvantage of increasing the number of components
In order to overcome the aforementioned disadvantages, an object of the present invention is to provide an image reading device that can be made smaller and that can read images at high image quality.
A first aspect of the present invention is an image reading device which reads an image recorded at an original, using visible light for reading the image and invisible light for detecting inappropriate pixels, and corrects inappropriate pixels of image data, including: a light source formed by light emitting diodes which emit visible light for reading the image and invisible light for detecting inappropriate pixels; an area sensor which reads the image by receiving light that has been one of transmitted and reflected by the image; and an image processing section which detects inappropriate pixels on the basis of invisible light image data, which has been read by invisible light at the area sensor, and corrects the inappropriate pixels at visible light image data, which has been read by means of visible light.
Operation of the first aspect of the present invention is explained below.
Visible light for image reading illuminates the original from the light source, visible light that is one of transmitted and reflected by the original is incident at the area sensor, and the visible light image data is read. Then, invisible light for inappropriate pixel detection illuminates the original from the light source, invisible light that is one of transmitted and reflected by the original is incident at the area sensor, and the invisible light image data is read.
Output of a wavelength in the invisible light region is not altered by image information at the original, but is altered by scattering if there is a scratch or the like at the original. On the other hand, a wavelength in the visible light region can reliably read the image at the original but, if there is a scratch or the like at the original, a scattered element is included in the image data that is read, and cannot be identified.
Accordingly, at the image processing section, inappropriate pixels of the image are detected from output alterations of the invisible image data. Inappropriate pixels of the visible image data corresponding to the same image are corrected by a method such as interpolation or the like. Hence, by illuminating the original with invisible light for detecting inappropriate pixels (in addition to the visible light for image reading), inappropriate pixels are accurately detected. Then, by correcting the visible light image data for the inappropriate pixels, high quality image reading can be carried out.
Moreover, because an area sensor is used for image reading, processing can be performed quickly.
Furthermore, because the light source is formed of light emitting diodes, it is smaller than a halogen lamp or the like. Moreover, filters and the like that transmit only one of visible light and invisible light are not needed. Thus, the number of components is decreased and costs are reduced. Moreover, the light emitting diodes emit little heat. Thus, image reading is not affected by heat from the light source.
A second aspect of the present invention is an image reading device according to the first aspect wherein the light source is formed by light emitting diode elements that emit visible light and which are disposed in array form, and light emitting diode elements that emit invisible light and which are disposed in array form.
Operation of the second aspect of the present invention is explained below.
The light emitting diode elements that emit visible light and the light emitting diode elements that emit invisible light are disposed in an array. Thus, a frame image is illuminated with different types of light. Thus, image reading and inappropriate pixel detection can be performed.
A third aspect of the present invention is an image reading device according to the second aspect wherein the light source is formed by light emitting diode elements of each of at least four wavelengths, including at least three visible light region wavelengths and one invisible light region wavelength, the light emitting diode elements of each wavelength being arranged in a pattern which is planar and which is the same as patterns of the light emitting diode elements of other wavelengths.
Operation of the third aspect of the present invention is explained below.
The three wavelengths in the visible light region may be, for example, three primary colors for reading the image at the original as a full-color image. The wavelength in the invisible light region is one of infrared light and ultraviolet light. Light emitting diodes that emit light of each of these wavelengths are disposed in planar patterns that are respectively the same as each other. Thus, unevenness is suppressed in the same way for each illumination.
A fourth aspect of the present invention is an image reading device according to the second aspect wherein the light source is formed by a plurality of types of light emitting diode elements disposed in rows and columns, which types of light emitting diode element respectively emit at different wavelengths, and the types of light emitting diode element are disposed alternately in at least one direction of a direction of rows and a direction of columns, and a ratio of a spacing between adjacent light emitting diode elements in the one direction to a spacing between adjacent light emitting diode elements in another direction is 1:(number of types of light emitting diode element).
Operation of the fourth aspect of the present invention is explained below.
The plurality of types of light emitting diode element that emit different wavelengths are disposed alternately in the one direction; for example, a vertical direction. The spacing between adjacent light emitting diode elements in a horizontal direction (the other direction) is a multiple of the spacing between adjacent light emitting diode elements in the vertical direction (the multiplier being the number of types of light emitting diode element). Consequently, horizontal and vertical spacings between light emitting diode elements that emit a respective wavelength are equal (1:1). Thus, unevenness of illumination by each wavelength at the area sensor is suppressed.
A fifth aspect of the present invention is an image reading device according to the third aspect, wherein the light source is formed by light emitting diode elements disposed such that distributions of light of respective wavelengths are uniform.
Operation of the fifth aspect of the present invention is explained below.
Because of such an arrangement, unevenness of illumination at the area sensor by light of a particular wavelength, which is emitted by light emitting diode elements of the respective wavelength, is suppressed.
A sixth aspect of the present invention is an image reading device according to the first aspect wherein the light source has a central portion and a peripheral portion, and the light emitting diode elements that form the light source are disposed more densely at the peripheral portion than at the central portion.
Operation of the sixth aspect of the present invention is explained below.
In a case in which the light source is a plurality of uniformly disposed light emitting diodes, the amount of light illuminating the original from the light source is less at peripheral portions than at the center. Hence, unevenness of illumination can be suppressed by the light source having a structure in which light emitting diodes are disposed more densely at the periphery than at the center.
A seventh aspect of the present invention is an image reading device according to the first aspect wherein the light source has a central portion and a peripheral portion, the light source is formed by a plurality of light emitting diode elements that emit visible light and a plurality of light emitting diode elements that emit invisible light, and, of light emitting diode elements that are disposed per unit area, the proportion that are light emitting diode elements that emit invisible light increases from the central portion to the peripheral portion of the light source.
Operation of the seventh aspect of the present invention is explained below.
The invisible light is less diffusive than the visible light. Therefore, there is a greater difference in the amount of light between the center and the periphery for invisible light than for visible light. Hence, the difference in amounts of invisible light between the center and the periphery can be suppressed by the proportion of the light emitting diode elements that are light emitting diode elements that emit invisible light increasing from the center to the periphery.
An eighth aspect of the present invention is an image reading device according to the first aspect, further including: a mirror box between the light source and the original, the mirror box having an internal reflection surface which reflects light from the light source, the mirror box thereby illuminating the original, and the mirror box having an entrance opening at which light from the light source enters the mirror box; and a diffuser provided at the entrance opening, the diffuser having a central portion and a peripheral portion, and having higher diffusiveness at the central portion than at the peripheral portion.
Operation of the eighth aspect of the present invention is explained below.
Because a diffuser that has higher diffusiveness at the central portion than at the periphery is provided at the entrance opening of the mirror box, of light entering the mirror box, light is diffused most at the central portion, where amounts of light are greatest. Thus, unevenness of illumination onto the original is suppressed.
A ninth aspect of the present invention is an image reading device according to the first aspect, further including: a mirror box between the light source and the original, the mirror box having an internal reflection surface which reflects light from the light source, the mirror box thereby illuminating the original, and the mirror box having an emergence opening at which light leaves the mirror box toward the original; and a diffuser provided at the emergence opening, the diffuser having a central portion and a peripheral portion, and having higher diffusiveness at the central portion than at the peripheral portion.
Operation of the ninth aspect of the present invention is explained below.
Because a diffuser that has higher diffusiveness at the central portion than at the periphery is provided at the emergence opening of the mirror box, of light illuminating the original from the mirror box, light is diffused most at the central portion, where amounts of light are greatest. Thus, unevenness of illumination onto the original is suppressed.
A tenth aspect of the present invention is an image reading device according to the eighth aspect wherein the diffuser is a diffusion member provided centrally at the entrance opening, the diffusion member and the entrance opening each having a peripheral edge spaced apart from one another.
An eleventh aspect of the present invention is an image reading device according to the ninth aspect wherein the diffuser is a diffusion member provided centrally at the emergence opening, the diffusion member and the emergence opening each having a peripheral edge spaced apart from one another.
Operation of the tenth and eleventh aspects of the present invention is explained below.
Because the diffusion member is provided only at the central portion of the entrance opening or emergence opening, of the light that enters or leaves the mirror box, light is diffused only at the central portion, where amounts of light are greatest. Thus, unevenness of illumination onto the original is suppressed.
A twelfth aspect of the present invention is an image reading device according to the eighth aspect wherein the diffuser is a diffusion member provided at the entrance opening, said diffusion member having a central portion and a peripheral portion, and said central portion being thicker than said peripheral portion.
A thirteenth aspect of the present invention is an image reading device according to the ninth aspect wherein the diffuser is a diffusion member provided at the emergence opening, said diffusion member having a central portion and a peripheral portion, and said central portion being thicker than said peripheral portion.
Operation of the twelfth and thirteenth aspects of the present invention is explained below.
Because the diffusion member provided at the entrance opening or emergence opening is thicker at the central portion than at the periphery, of the light that enters or leaves the mirror box, light is diffused most at the central portion, where amounts of light are greatest. Thus, unevenness of illumination onto the original is suppressed.
A fourteenth aspect of the present invention is an image reading device according to the first aspect, further including: a mirror box between the light source and the original, the mirror box having an internal reflection surface which reflects light from the light source, the mirror box thereby illuminating the original, and the mirror box having an entrance opening at which light from the light source enters the mirror box and an emergence opening at which light leaves the mirror box toward the original; and an ND filter provided centrally at one of the openings, the ND filter and the one of the openings each having a peripheral edge spaced apart from one another.
Operation of the fourteenth aspect of the present invention is explained below.
Because the ND filter is provided only at the central portion of the entrance opening or emergence opening, of the light that enters or leaves the mirror box, amounts of light transmitted are reduced at the central portion, where amounts of light are greatest. Thus, unevenness of illumination onto the original is suppressed.
A fifteenth aspect of the present invention is an image reading device according to the first aspect, further including: a mirror box between the light source and the original, the mirror box having an internal reflection surface which reflects light from the light source, the mirror box thereby illuminating the original, and the reflection surface being formed by a diffusion member.
Operation of the fifteenth aspect of the present invention is explained below.
Because the reflective surface inside the mirror box is formed by a diffusion member, diffusion of light at the mirror box is greater. Thus, unevenness of illumination onto the original is suppressed.
A sixteenth aspect of the present invention is an image reading device according to the first aspect wherein the area sensor is formed by imaging elements and an amount of light received by the area sensor is controlled by means of controlling an accumulation time of the imaging elements.
Operation of the sixteenth aspect of the present invention is explained below.
By controlling the accumulation time of the imaging elements at a time of fine-scanning, insufficiencies of light of each wavelength can be corrected. For example, a shortage of blue light can be corrected for by increasing the corresponding accumulation time.
A seventeenth aspect of the present invention is an image reading device according to the first aspect wherein an amount of light received by the area sensor is controlled by means of controlling driving factors of the light emitting diodes.
Operation of the seventeenth aspect of the present invention is explained below.
By controlling the driving factors of the light emitting diodes at a time of fine-scanning, insufficiencies of light of each wavelength can be corrected. For example, if blue light is insufficient, the amount of light can be increased accordingly by increasing the driving factors (e.g., current) of the corresponding light emitting diodes rather than increasing the accumulation time at the area sensor. That is, inadequate amounts of light can be corrected for without increasing image reading time.
An eighteenth aspect of the present invention is an image reading device according to the first aspect, further including: a correction section that stores in advance respective shading correction values corresponding to different wavelengths of light emitted from the light source, and corrects shadings of image data read respectively at each wavelength on the basis of the shading correction values.
Operation of the eighteenth aspect of the present invention is explained below.
Shading correction can be performed by correcting the image data that has been read on the basis of the shading correction values that were set in advance.
A nineteenth aspect of the present invention is an image reading device according to the first aspect wherein shading correction is performed by reading an image in a state in which the original is not present, and separately controlling output of each light emitting diode element on the basis of an output value of the area sensor.
Operation of the nineteenth aspect of the present invention is explained below.
Image reading is performed without the original being present, and each light emitting diode is respectively separately controlled on the basis of the obtained image data (unevenness of illumination). The light source is actually a collection of point light sources. Thus, the amount of light from each point light source can be controlled and unevenness of illumination can be suppressed (shading correction can be performed).
A twentieth aspect of the present invention is an image reading device according to the first aspect, further including: a photoelectric transducer that detects an amount of light between the original and the light source, wherein output of the light emitting diodes is kept constant on the basis of output of the transducer.
Operation of the twentieth aspect of the present invention is explained below.
Feedback control is performed on the basis of amounts of light of each wavelength emitted from the light emitting diodes. Thus, changes in brightness when the light emitting diodes are lit can be suppressed.